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Helium Rich Subdwarf O Stars and Central Stars of Planetary Nebulae*

Published online by Cambridge University Press:  12 April 2016

R.H. Méndez ,
C.H. Miguel ,
U. Heber  and
R.P. Kudritzki
R.H. Méndez
Affiliation:
Instituto de Astronomía y Física del Espacio, C.C. 67, 1428 Buenos Aires, Argentina
C.H. Miguel
Affiliation:
Instituto de Astronomía y Física del Espacio, C.C. 67, 1428 Buenos Aires, Argentina
U. Heber
Affiliation:
Institut für Theoretische PhysikundSternwarte der Universität Kiel, Olshausenstrasse 40, D-2300 Kiel, Federal Republic of Germany
R.P. Kudritzki
Affiliation:
Institut für AstronomieundAstrophysik der Universität München, Scheinerstrasse 1, D-8000 München, Federal Republic of Germany

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In this review we will discuss the hottest subluminous H-deficient stars, namely those with Teff > 30000 K. In the absence of reliable distance determinations for hot subluminous stars, the best way to discuss their properties and evolutionary status is to find their positions on the log g - log Teff diagram. In the last few years, after extensive computational work, first in Kiel and more recently also in Munich, it has become possible to obtain log g and Teff, together with the surface He abundance, directly by fitting the observed H and He absorption line profiles with theoretical profiles obtained from non-LTE model atmospheres and associated line formation codes. The non-LTE models are plane-parallel, in hydrostatic and radiative equilibrium, and the atmosphere is assumed to consist of H and He only. A recent paper by Groth et al. (1985) gives most of the references on the application of this non-LTE model atmosphere approach to the study of all kinds of hot subluminous stars.

Type
VII Related Objects
Information
International Astronomical Union Colloquium , Volume 87: Hydrogen Deficient Stars and Related Objects , 1985 , pp. 322 - 343
Copyright
Copyright © Reidel 1986

Footnotes

1

Visiting Astronomer, Cerro Tololo Inter-American Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the U.S. National Science Foundation.

2

Member of the Carrera del Investigador Científico, CONICET, Argentina.

*

Based partly on observations collected at the European Southern Observatory, La Silla, Chile.

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